BHP shares have jumped more than four per cent after the mining giant said it would return $US10.4 billion ($A14.7 billion) to shareholders in the form of an off-market buyback and special dividend.

BHP's ASX-listed shares were 4.4 per cent higher after 20 minutes of trade on Thursday following an announcement that the world's biggest miner would immediately start a $US5.2 billion buyback.

The company, which in July promised to give shareholders the $US10.5 billion generated by the sale of its US onshore sale assets, says $US5.2 billion will then be returned via a special dividend to be calculated on December 17 - following the completion of the buyback.

Chief executive Andrew Mackenzie, who announced the move after BHP completed the sale of its interests in Eagle Ford, Haynesville and Permian Onshore US oil and gas assets to BP's local unit, says shareholders will have pocketed $US21 billion over two years once the cash is handed over.

"We made a commitment that all the net proceeds from the disposal of our onshore US assets would be returned to shareholders and we are honouring that commitment now that the sale transactions have been completed," Mr Mackenzie said in a statement.

Australian shares are ahead at the open following BHP’s announcement and overnight gains on Wall Street.

AMP shares also soared early on speculation Macquarie Group was eyeing a takeover, with stocks in the under-fire wealth manager up by as much as 7.7 per cent early to $2.66.

The wider financial sector is up, with NAB rising 1.13 per cent to $25.495 on the positive news buried within the announcement of a 14.2 per cent drop in full-year profit due to restructuring costs and customer remediation.

Commonwealth and Westpac are down 0.27 and 0.07 respectively, but ANZ gained 0.35 per cent to $26.02 after Wednesday's beating.